A dispenser for continuously dispensing a specified quantity of resin in the course of producing electronic parts is extensively used in a semiconductor manufacturing process. The resin used in the semiconductor manufacturing process serves to bond, cover and protect a semiconductor device. Examples of the dispensing step include an underfill step and an LED mold formation step, which steps are automatically performed by a resin-applying dispenser.
In particular, the dispensing step is essential in an LED manufacturing process in order to dispense silicon containing a fluorescent material on a package provided with an LED chip to thereby adjust the color of light emitted from the LED chip and to structurally stabilize the LED chip.
It is of paramount importance that an accurate quantity of resin is applied on workpieces in the LED mold formation step or the underfill step. If the dispensing quantity of resin is inaccurate, it may be a cause of generating defective products. This results in reduced productivity and increased manufacturing cost.
Conventionally, the dispensing quantity of resin is controlled by measuring the weight of the dispensed resin with a scale and feeding the measurement result back to a dispensing control unit.
It is however typical that the minimum weight measurable through the use of a scale is greater than the minimum dispensing quantity of resin adjustable by the pump of a dispenser. This limits the accuracy of measurement made by the scale, which necessarily reduces the accuracy of controlling the dispensing quantity of resin. In case of using a jet-type pump, the dispensing quantity is controlled by counting the number of droplets dispensed. In general, the minimum weight measurable with the scale is greater than the weight of one of the droplets. This means that the dispensing quantity cannot be adjusted on a droplet-by-droplet basis according to the scale measurement method. When using a screw-type pump, it is general that the quantity of the resin dispensed in proportion to the rotational angle of a screw cannot be accurately measured with a scale.
A high precision scale may be used to accurately control the dispensing quantity of resin. However, this poses a problem in that the total manufacturing cost of the dispenser becomes quite unreasonable. In addition, use of the scale imposes a restriction on the weight measurement speed, consequently reducing the overall manufacturing speed.